Telephone system



INWAPD JACK OFFICE X ouTwARD Aem Dec. 16, 1924. 1,519,497

H. D. MaCPHERSON TELEPHONE SYSTEM Filed Jan- 5, 1922 8 sheets-Sheet 1 Dec, 16, 19:24. 1,519,497

H. D. MaC-PHERSON TELEPHONE SYSTEM Filed Jan. 1922 e sheets-sheet 2 y www /m/e/7 far.'

Dec, 1 6, l 924.

H. D. MaCPHERSON TELEPHONE SYSTEM Dec. 16, H. D. MaCPHERSON TELEPHONE SYSTEM OFFICE Y H. D. MaCPHERSON TELEPHONE SYSTEM Dec, 16, 1924. 1,519,497

Filed Jan 5, 1922 8 Sheets-Sheet 5 Dec. 16, l924'- 1,519,497 H. D. MacPHERsoN TELEPHGNE SYSTEM Filed Jan- 5, `1922 f8 sheets-sheet s Dec. 16, 1924. 1,519,497

H. D. MaCPHERSON TELEPHONE SYSTEM l I Filed Jan 5, 1922 8 sheets-sheet v z E? r 153 v AIl Il I H Sw f7 7 offici Z INWAQD JACKS OUTWARD JACKS Dec. 16, l 924.

H. D. MaCPHERSON TELEPHONE SYS TEM Filed Jan- 1922 8 sheets-sheet a w w mw uw w@ w@ www RQ w@ n@ E@ www@ l, M f @Q W Mew. d VQ NS?. $9, la@ 5% i Nv Wl Mmm-*F\\m.\n El Awww SM ,i 1 L @u QN Patented Dec. i6, 1924i@ LEMAN' nrltifi PATENT OFFE.

HUGH D. IACPHERSON, OF SUMMIT, NEW' JERSEY. ASSGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEVJ YQRK. N. A. CORPORATON F NEW YORK.

TELEPHONE SYSTEM.

Application filed January To all whom t may conce/rfa Be it known that l, HUGH D. MAGPHER- soN, a citizen of the United States, residing at Summit, in the county of Union, State ot' 5 New Jersey, have invented certain new and useful Improvements in rlelephone Systei'ns, of which the following is a full. clearA concise, and exact description.

This invention relates to improvements in telephone systems and has particular reference to a system wherein signals for a plurality of toll lines extending between widely separated offices are transmitted over a signaling pat-h common to said toll lines.

The present invention contemplates a toll switching` system wherein connections are extended 'from one terminating office to another over sectionalized toll lines which are joined to an intermediate office to which calls may also be extended 'from either of thc terminating offices. ln a system of this character it is desirable7 when any one of the plurality of toll lines interconnecting the terminating and inter- 5 mediate oflices is taken for use. to indicate the busy condition of such line at the various ofces.

An object of the invention is to transi'nit code impulses over a common patli for operating certain signals to indicate at distant offices the busy condition of the toll line taken for use and also for operating a signal individual to said line before an operator at. the office which is called.

Another object is to selectively signal a particular one of a plurality of operators at either terminating office over any one of said toll lines and to operate at the terminating and intermediate offices the busy signals of the line taken for use. A further object is the provision of a plurality of `signals for each toll line at certain offices which are selectively operable codes of transmitted inipulses having different characteristics which are determined by the cooperation of selec-- tive switches, said codes being individual to the particular line taken for use.

These and other objects of the invention not specifically mentioned above will clear- 50 ly appear from the following description and drawings. Figs. l to 8 of which`r when arranged in accordance with Fig. 9. illustrate a preferred embodiment of the invention.

ln carrying` out the invention each toll line of a `group is preferably provided at each terminating ofiice with a plurality of terminals or jacks, certain of which are employed for outgoing traflicu while others are utilized for incoming traffic. F or outgoing traffic, the originating operator has access to three jacks for each line7 two of which are einployed for calling the distant terminating office, while the remaining one is used when signaling the operator at thel intermediate of lice. lf the call is an original one to be extended to the distant terminating office, the operator at the calling oi'lice inserts the plug of a cord circuit into what is designated as the outward in jack on the drawings (Figs. l and 7). This causes the transmission of current impulses over a path common to the toll lines of a group and joining the calling office with the intermediate and distant terminating ofiices. This code of impulses is individual to the line taken for use and the particular operator at the terminating office with whom it is desired to establish connection. Current impulses are transmitted and received by means of start-stop distributors, and upon being received at the intermediate oflice are translated. in a well-known manner, to effect the operation of signals at the intermediate office which indicate thcreat the busy condition of the toll line which has been taken for use. The impulses are repeated at the intermediate office and transmitted to the called terminating office and upon being received thereat are again translated to actuate certain mechanism which controls the operation of a line signal associated with the inward in ack.

Under certain traffic conditions to be later explained in detail, it is necessary that the line signal individual to the line taken for use and to the inward out jack at a terminating office be operated. ln this event plug is inserted in the outward out 'jack at one terminating office. whereupon a code of impulses individual to thel line taken for use and to the inward out7 liack at the other terminating office is transmitted over the common signaling path to again operate the busy signals at the intermediate office. where the code is again repeated and transmitted to the last-named terminating ofiicc to effect the operation of the line signal ther-eat individual to the line taken for use and the inward out jack, and also to operate the busy signals for the line at the .last-mentioned terminating office.

Vhen calling the intermediate office from either terminating office, the operator connects a cord circuit to the: outward through jack. The signal before the through operator at the intermediate omce individual to the line taken for use, together' with the busy signals for said line at said office. are thereupon operated by a code of impulses transmitted from the originating ofiice. This code is repeated at the intermediate ofiice and transmitted to the other terminating office to cause the operation of busy signals at the latter office individual to the seized line.

In order to accomplish the signaling of the various positions indicated by the jacks at the terminating and interniediate offices, each toll line has three sets of code impulses individual thereto, one each for the line signals assigned to the inward in and out jacks at the terminating offices and the jacks at the intermediate office. To produce these various code signals the present invention preferably makes use of four rotary switches see Figs. 2 and 6) associated with each sending distributor employed, all of these switches being common to a group of toll lines. Each one of three of said switches is individual to one of the positions to be called, while the fourth switch is common to said positions. When a call is initiated on any particular line of the group served by said switches, the wipers of the first three mentioned switches are operated to select the terminals of their banks individual to the seized line, whereupon the fourth switch is actuated to step its wipers to terminals individuali to the position being called. Then through the wipers of the switch of the first three mentioned which is individual to the position called, and through the wipers of the fourth switch, certain battery potentials which determine the code of impulses to be transmitted. are connected to the sending segments of the start-stop dfstributor.

It is believed that the invention will now be fully understood from the following detailed description of the various operations in establishing and disconnecting' calls between the different oi'iices.

Operator at oyjce initiates fr (fra/ZZ to of- ]icc Z.

/Vhen the toll operator at office X desires to establish a connection to the inward operator at ofi-ice Z, the plug 100 of an operators cord circuit A is inserted into the in jack 101 of the outward acks associated with an idle toll line L. The cord circuit A may be of a type well known in the art and only so much of this circuit is shown as is necessary to an understanding of the operation of this system. It is understood that this cord circuit is employed to connect the toll operator with the calling subscriber and afterwards to complete the connection between the calling and called subscribers over the toll line L. The connection of the cord circuit A with the toll line L is designed to transmit a code of impulses from the oihce X through the intermediate or through office Y to the terminating office Z, which code of impulses results in the operation of signals at the. intermediate or through office to indicate the busy condition of the line L which has been selected and to also operate a signal before the incoming operator at ofiice Z to indicate that a call is awaiting attention on the line L. The insertion of plug 100 into the infjack 101 establishes a circuit extending from ground through the winding of the sleeve relay 102 of the cord circuit A, the sleeve contacts of the plug 100 and jack 101, the winding of relay 103 individual to the jack 101, and the left-hand winding of the common relay 101i to grounded battery. Relays 103 and 104C energize in this circuit and theclosure of the alternate contact of relay 103 establishes an obvious energizing circuit through the ri ght-hand winding of relay 105. `When relay 105 is energized relay 104i is locked in a circuit extending from grounded battery through the right-hand winding and alternate contact of relay 104, and the inner right-hand alternate contact of relay 105 to ground. The operation of relay 105 also establishes a circuit for operating the busy signal magnets 118, 119 and 120 to indicate the busy condition of the line L, said circuit eXtendng from grounded battery through the magnets 118, 119 and 120 in series, and the inner right-hand contact of relay 105 to ground. Slow release relay 120 is also energized at this time over a path extending from grounded battery through the winding of relay` 126, the normal contact of relay 129 and from thence over the locking circuit of relay 10%. The operation of relay 126 performs no function at this time.

The calling operator now depresses her ringing key 1410 in the cord circuit A., and in response to the connection of the ringing current to the toll line L the ringing relay 100, bridged across the line L, is operated. A circuit is thereupon established for the slow-to-release relay 107 extending from grounded battery through the winding of this relay and the contact of relay 106 to ground. The operation of relay 107 closes an energizing circuit for relay 108 extending from grounded battery through the right-hand normal contact of relay 109, the winding of relay 108, and the alterna-te contact of relay 107 to ground. Relay 108 energizes and locks through its inner left-hand alternate contact. The closure ot the inner right-hand alternate contact ot relay 108 establishes an ohvious energizing circuit for slow-to-release relay 110, which, in operating, locks through its inner lett-hand alternate contact to ground at the lett-hand normal contact ot relay 111. llllhen the outer right-hand contact ott relay 108 is closed ground is extended through the right-hand normal contact oli relay 111 to the outer right-hand contact ot relay 107 which relay is now energized. The closure et the outer lett-hand Contact of relay 108 connects ground to the inner right-hand armature of relay 107. lllhen the operator releases the ringing key, relay 106 deenergizes to open the energizing circuit tor relay 107, which, after an interval, restores. rlhe opening ot the alternate contact ot relay 107 breaks the original eue gining circuit tor relay 108, hut this relay remains locked through its inner lett-hand contact. The closure et the inner right-hand contact ot relay 107 connecte ground to the start conductor 112 which extends to the contact ot relay 200 and from thence in multiple through the normal contacts ot relays 201, 202 and 208 to the contacts and windings oi the motor magnets 201i, 205 and 206, respectively, of the rotary switches B, C and l). The ground connected to the outer right-hand contact ot relay 107, by the closure ot the outer right-hand contact ot relay 108, is ertended, when relay 107 releases, through the outer right-hand contact et relay 105, which is now energized and locked through its lett-hand winding and inner lett-hand contact to the outer letthand contact oit relay 110, to the individual conductor 118 ot the toll line L, which is connected to a terminal ot the switch l) over which the wiper 207 passes. lt is to he noted that the other condi, ctors 111i and 115, individual to the toll line li and connected, respectii/"elyA` to terminiiils of the switches C and B, are not grounded since relays 116 and 117, similar to relay 105, are not operated. The conductors 113, 111i and 115 are connected, respectively, to correspoi'iding terminals in the banks ot switches D, C and B over which the wipers 207, 208 and 209 pass, and these corresponding terminals are each individual to the toll line L which has been selected tor use. the other terminals ot said banks lacing individual to other similar toll lin lWhen the start conductor 112 is grounded, as previously described, circuits are closed 'tor the stepping magnets 204;, 205 and 206 ot the switches ld, C and l), and the wiper-s ot these switches are stepped over their associated terminals. This stepping action continues until the wiper 207 ot switch D engages the terminal to which conductor 13 is connected. rThis conductor being now grounded,7 when wiper 207 engages said terminal the ground will be extended therethrough to the lett-hand winding ot relay 209i and trom thence to grounded loattery. Relay 208 energizes to permanently open the circuit oit the stepping magnet 206. ln closing its inner lett-hand contact relay 20? est-ahhUA \s an energizing circuit ttor relay 200 which operates to disconnect the start conductor 112 trom the windings oi the various stepping magnets. rlhese magnets now cease to operate and bring the wip-- ers oil the switches B, C and D to rest upon the associated terminals individual. to the toll line L. The larmnul which is connected to the inner lei and contact ot relay 203 is also extended through the noriaal contact of relay 210 and the Contact and winding ci the stepping magnet 211 ot the rotary switch rllhe stepping); magnet 211. therefore, operates and 203- is energized and steps the wipers o' switch E until the wiper engages a terminal to which ground is connected. ln the present instance grounc is connected thi'ougjgh tue wiper 207 and terminal engaged thereby, the right-hand contact of relay 208 to the lirst, fourth and seventh. terminals ot the row over which wiper 212 passes. rllliere'liore, with the wiper 212 in the position shown in the drawing it will he apparent that the same will be caused to talo only one step, whereupon the ground connected to the it'ourth terminal then engage/d will be extended through the letthand winding ot relay 210 to grounded hattery to energize this relay and open, at its lett-hand Contact, the circuit for the stepping magnet 211, which thereupon ceases to operate. The wipers ot switch E are nouv brought to rest on terminals which are individual to the switch l), this latter switch heing the one which. controls the character ot certain ot the impulses oit the code to he transmitted to the terininat' ,g otlice Z when the inward operator at said oliice is being called. ln like manner the switches C and B control the character ot certain ot the impulses of the codes transmitted from the originating oliice when the outward operator at the terminating oiiice or the through 0perator at the intermediate ollice is heing called. With the wipers ot switch E engaging terminals individual to the switch D, it will he obvious that only the polarities connected to the terminals engaged by the wipers 213, l, 215, 216 and 217 olE switch l) will he etlective in determining' certain olf the impulses ol the code to be transmitted. The code transmitted in each instance consists ot eight impulses seven oli which are determined by the polarities connected to wipers 219 to 225 inclusive ot the switch l0, the eighth impulse being determined hy the condition ot the relay 243 associated with the sending distributor SD, which is ot the usual start-stop type such as employed in printing telegiaphy. The sending distributor tion.

SD is connected to a receiving distributor RD at the intermediate or through otce Y over a common signaling path or conductor P Which terminates in the windings oi? pola-r relays 250 and 450. In order that the transmitted code combinations may be translated into suitable signals for appropriate toll lines and the desired operators position at the distant cnice, the invention preferably provides a receiving apparatus asociated with the receiving distributor RD which is selectively' responsive to the transmitted code combinations to etl'ect the operation or the proper signals. This receiving apparatus, as herein shown at the intermediate station Y, includes a plurality of locking relays 100 to 407, the locking circuits of Which are controlled by common relay 408. The apparatus 'further includes a pyramid relay combination of a type Well known in the signaling art, the relays of this combination being indicated by the numerals ll09 to 432 inclusive. In accordance With the code o'l impulses transmitted, the apparatus, including the locking and pyramid relays, responds to provide a path through contacts oi said relays over which the signals individual to the selected toll line and operatorys position are transmitted.

The apparatus is noW in condition to F transmit the code of impulses individual to the line L and to the in operators position at oliice Z to the receiving mechanism at the intermediate oiiice Y. `With the brush 227 of the sending distributor SD in its normal position a circuit is established, upon the energization of relay 210 as previously described, extending from grounded battery through the start magnet 228 oit the sendingdistributor, the right-hand contact of relay 210, the start segment 229, the brush 227 and the ring 230 to ground. Magnet 228 energizes in this circuit to release brush 227, which thereupon makes a complete revolu- When brush 227 is disengaged from the start segment 229 shortly after the beginning of its revolution, the circuit for the start magnet 228 is opened and this magnet releases to permit its armature to move into the path of the brush 227 so that when the latter completes its revolution it is stopper. by said armature. Upon engagement ot brush 227 With segment 231 at the beginning of the revolution of the brush, a circuit is established from thev positive pole of battery through segment 231, brush 227, ring 232, and thence over one path through the lower Winding of polar relay 250 and the artificial line to ground, and over another path through the upper Winding ot relay 250, the common conductor P and both windings ot polar relay LL50 to ground through tie artificial line. The closure oit this circuit has no eiect upon the polar relay 250 but causes the relay 450 to close its lower contact, whereupon a circuit is established from grounded battery through the lower contact o'ii relay 450, the segn nt ot' the receiving distributor RD, brush thereof, segment 43a, and the winding of start magnet 430 to ground. The closure of this circuit energies the magnet to release brush 431i, which thereupon maires a complete revolution in synehronism with the brush 227 of the sending distributor SD. rl'he disengagement of the brush e134 from segments rofl and at the beginning oi the revolution of the brush opens the energizing circuit ior magnet Lil-3G which thereupon releases so that its armature will stop the brush o23-'lf at the completion ot the revolution. l*Vith the brushes ot the sending and receiving distriliiutors non' revolving' in synchronism, the code of impulses determined by the positions of the Wipers ot switches D and E is noiv transmitted.

jitter passing from engagement with the wipers 229 and 231, the brush 227 engages segment thereby establishing a circuit extending from ground through the ring 230, brush 227, segment 233, and the righthand winding of relay 210 to grounded battery. This circuit also extends in multiple through the Wiper 218 and the fourth terminal in its associated row, and from thence through the right-hand Winding of relay 203 to grounded battery. This circuit turther extends in multiple through the Wiper 23d of switch D, and through the Winding ot relay 109 to grounded battery. Relays 210 and 203 are maintained energized as long as brush 227 is in engagement With the segment and relay 100 is energized in the circuit described therefor and remains energized contemporaneously with the relays 210 and 203. rlhe energization of relay 109 opens, at its right-hand contact, the locking circuit for relay 108 and this relay thereupon restores. The release of relay 108 removes ground from the conductor 113 connected to the terminal novv engaged by Wiper 207 of switch D, thereby opening` the original energizing circuit for relay 203, but this relay remains energized in the circuit through its right-hand Winding. The release of relay 108 also removes ground from the start conductor 112 to prevent any further operation oi the stepping magnets 204i, 205 and 206 When relay 200 releases, Which release occurs When the relay 203 deenergizes at the termination of the revolution of the brush 227, that is, when said brush disengages the segment 233.

At the saine time that segment`233 is engaged by brush 227, segment 235 is also engaged and a circuit is thereupon established eatending from the negative pole of battery through the wiper 210 ot switch lll and fourth terminal engaged thereby, segment 235, brush segment the upper winding of polar relay 250, common conductor l), and the windings of polar relay 450 to ground. rflic impulse ot negative polarity transmitted over the path. l by the closure ot this circuit operates the polar relay 450 to cause the same to close its upper contact. it the time that this impulse is transmitted brush 434 is in engagementwith the ments 437 and 438. the latter segment being connected to the lett-hand winding` ot the iirst locking` relay 400. The closure ot the upper contact ot relay 450 therefore establishes a circuit extending from grounded battery through the upper contact of relay 450, segment 437, brush 434, segment 42%, and the lett-hand winding ot locking relay 400 to ground. Relay 400 operates and locks through its right-hand winding and lett-hand contact to ground at the contact ot relay 40S which was energized over an obvious circuit when the brush arm 454 first engaged the segment 440. The brushes i227 and next engage, respectively, the segments 236 and 439. A. circuit tor transn'iitting the second impulse ot negative polarity for the signaling conductor l? is now established, said circuit extending` 'from the negative pole of battery through wiper 213 o't switch D and terminal engaged thereby. wiper 220 ol' switch E, segment 23o, brush. i127, segment 232, and from thence over the previously described path through the polar relays 250 and 450. rllhis impulse ot negative polarity maintains the upper contact oit' relay 450 closed whereupon a circuit is established from grounded battery through said upper Contact. segment 437. brush 434, segment and the lett-hand winding oi' rela r 401V to ground. Relay 401 e ergizes and loclrs through its right-hand winding and lett-hand contact to ground at the contact ot relay 408. The third impulse transmitted is ot positive polarity and the circuit therefor is closed when brushes and 434 engage, respectively. segments 237 and 441. The circuit for this impulse is traceable from the positive pole of battery through the wiper 214 of switch D, the wiper ot switch E, segment 23'?, brush 22?.. segment Q32, and from thence over the previously traced path through the polar relays and 450. Relay 450 operates to close its lower contact and hence no circuit, will be established tor the locking relay 402. The tourth impulse to be sent is oit negative polarity and is transmitted over the common path P when the brushes 227 and 434 engage, respectively, segments and 442. `When this occurs current ot negative polarity is connected through the wipers 215 and 922 of switches D and E and extended through segments 238 and :232 and the polar relay. L and The relay 450 closesI i ts upper contact in response to this impulse and thereby establishes an operating circuit for locking relay 40?) extending from grounded battery through the upper contact ot relay 450` segment 437, brush 434, segment 442, and. the lett-hand winding` of relay 403 to groiuid. 403, in energizing, locks through its right-hand winding and left-hand contact to ground at the contact,- oi' relay 408. The fifth ann sixth impulses transmitted arc. respectively, of positive and negative polarities and are sent when the brush 227 engages segments 2f-l0 and 240, at which time brush 434 engages segments 44? and 444. lt is believed that the establishment ot these circuits for the successive impulses will be clearly understood from the previous description. The 'litth impulse being ot positive polarity will tail to operate the locking relay 404. The sixth impulse ot negative polarity causes the operation ot locking relay 405 and the loci.:- ing` ot the same in a manner which is now believed to be obvious. The seventh impulse is determined by the position ot the wiper 225 which is now in engagement with the fourth contact of its associated row. to which negative polarity is connected. rthis seventh code impulse is transmitted when brushes 227 and 434 engage, respectively., segments 241 and 445. yllhe character ol' this impulse causes polar relay 450 to close its upper contact to establish an energizing circuit 'tor locking relay 406, which.. upon energizing, locks through its right-hand winding to the Contacty of relay 40S. The eighth and last impulse is transmitted when brushes 227 and 434 engage. respectively. the segments 242 and rlhe circuit tor this impulse extends trom positive pole ot battery through the normal contact ot relai' Q43, segn'ient242. brush 9,27. segment and from thence over the previously dscribcd path. This impulse being ot positive polarity prevents a circuit from being established tor the locking relay 407. As a result ot' the code oit impulses transmitted locking relays 400. 401. 403. 405 and 40 have been operated and locked.

At the termination or' the last impulse.y brush 22T passes trom engagement with the segment and thereby disconnects the holding ground trom the windings of relays 210. 20S and 109, which relays thereupon restore to normal. The release of relay 203 opens the holding circuit tor relay 200 which thereupon releases. rllhe apparatus is now in normal condition with the exception ot' the operation ot relays 103 104, 105 and 110 and the busy signals 118, 119 and 120.

At the same time that the brush 227 disengaees the segment 223, the same also disengages the segment 242 and then engages o o It i: 5:1

the segment 244 to cause the transmission of a negative impulse over the path P, which operates relay 450 to close its upper contact. At this time the brush 34 has disengaged segments 437 and 446 and hence the closure ot the upper contact ot relay 450 will have no effect.

rlhe result of the operation of the various locking relays will now be described. lli/Then the relay 400 operates, a circuit is established trom ground through the right-hand Contact ot relay 400 and the windings of pyramid relays 427 to 432 inclusive, in series to grounded battery. These relays energize and are held operated as long as the relay 400 remains locked. vThe operation ot relay 401 closes a circuit extending trom ground through the right-hand Contact ol' relay 401 and the windings ot relays 420 to 426 inclusive, in series to grounded battery. These latter relays also energize. When relay 408 operates an obvious circuit is closed tor energizing relays 412 to 415 inclusive. Relay 409 is also operated by the energize tion of the locking relay 405. Vfith the pyramid relays described as energized in their operated condition and upon engagement ot the brush 434 with segments 447 and 448, a circuit is established extending trom the negative pole ot 120 Volt battery through the normal contact of relay 407, segment 447, brush 434, segment 448, righthand alternate contacts ot relays 400 and 409, left-hand normal contact of relay 411` left-hand alternate Contact of relay 414, right-hand normal contact ot relay 418, the right-hand alternate contact ot relay 425, the lett-hand alternate Contact of relay 480, the conductor 449, and the left-hand winding` ot differential relay 500 to ground. This circuit energizes the relay 500 which then locks through its right-hand winding4 and contact. llfhen relay 500 closes its outer lett-hand alternate contact, the 120 Volt impulse of' current is transmitted to the right-hand winding of relay 507 causing this relay to energize. However, since no locking circuit tor relay 507 is established at this time, the relay 508 being released, relay 507 releases at the termination ot the impulse without performing any function. The energizing circuit for relay 500 is opened when the brush 434 passes trom en gagement with segments 447 and 448. At the same time, said brush disengages segment. 440, whereupon the circuit for relay 408 is opened and this relay releases ti; open the locking` circuits ot the relays 400, 401, 403, and 406, which relays therei upon restore. The -restoration of these re-v lays opens the circuits tor the various pyramid relays which have been operated `and these latter relays also release. The code o't impulses individual to the line L and to .the in operators position ,at ofi'ice Z has now been transmitted to the interd mediate or through ofiice Y.

Upon the energization of relay 500 in response to the impulse ot negative polarity transmitted over the conductor 449, a circuit is established for relay 504 extending from grounded battery through the right-hand winding ot relay 504, the inner lett-hand alternate contact of relay 500, and the outer normal contact of relay 509 to ground. Relay 504 energizes and therby established a circuit to operate the busy signal magnets 320 and 520 to indicate, at the intern'iediate olii-'ce Y, the busy condition ot the toll line L, said circuit extending from grounded battery through the .vindings ot magnets 320 and 520 in series, and the outer lett-hand contact ot relay 504 to ground. The energization of relay 504 also closes a circuit traceable trom grounded battery through the right-hand contact ot relay 516, winding ot relay 517, the right-hand normal contact of relay 518, the outer right-hand contact ot relay 504.` and the outer normal contact oi relay 509 to ground. Relay 517 energizes in this circuit and locks to ground through its winding and inner lett-hand contact. The closure ot the outer lett-hand contact oi relay 517 establishes an obvious energizing circuit tor relay 519 which thereupon energizes and loclts through its letthand Contact to ground at the lett-hand normal contact of relay 521. rlhe energization oit relay 519 establishes a circuit ent-ending from ground through the outer righthand contact ot relay 519, and trom thence over one path through the normal contacts ot relays 503 and 507 and winding of slowto-release relay 008 to grounded battery, and over another path through the normal corn tacts oit relays 3053 and 307 to grounded battery through thel winding ot the slow-torelease relay 308. The relays 308 and hl energize in this circuit but pci'i'orni no tuurtions at this time.

lf'llhen relay 517 operates, ground is connected through the inner right-hand contact ot this relay and the lett-hand normal contact ot slowtorelease relay to start conductor 512, which is connected, through the contact ot relay 600 and the lett-hand normal contacts of relays 601, 602 and 603, to the windings ot' the stepping magnets 604, 605 and 006 otl the switches l, C and D. The closure of the outer right-hand 'contact ot relay 517 entends the ground connected to this contact through the right-hand normal contacts ot relays 521 and 522, the inner right-hand contact ot' relay 504, and the indivvidual conductor 513 to the terminal individual to the toll line oyer which the wiper 607 et switch. D passes. Stepping magnets 604, 605 and 606 operate upon the grounding ot conductor 512 to step the wipers ot their respective switches until the wiper 607 enswitches l. C" and D are thereupon brought to rest upon ternnnals individual to line A code ot impulses nouv transmitted 'troni the ottico Y to the oilice and translated by the receivingv mechanism oi Fig'. Q to select the conductor Sel-Sl. The operation iu connection with the transmission oi this code ot impulses is precisely the saine as that described in connection with the transmission and reception oi" the codo of in'ipulses trom olhce X to oilice Y by the sending; and riweiyiira ine r-luuiisms ot 2 and el. lnasiuuch as the mechanism ot lFigs. 2 and (i and Figs. -l and 8 are duplicates and the rehuence characters applierL to like parts in duplicate (injures are the saine with the e-ception oit the hundreds digits, it is belie'ved that the operation ot the transmission ot the code ot impulses trom oiiice Y to oliice Z will he tully understood by reierence to the previous description. During' this operation brush G27 ot' the filistributor Si 1 engages the ring G30 and segment to connect Igjround through wipers G18 and to the Winding' ot relay 516, whereupon this relay energizes and remains operated as long as brush i327 is in engagement with the segment 53?. The energization or relay 516 opens the locking' circuit for relay 517 which thereupon restores to open the original energizing circuit for relay 519. The latter relay, however, remains energized over the locking' circuit described therefor. The ene ero'izatiou ot relay 516 also establishes a circuil extending" from A ounded liatterji' through the alternate contact ol relaf,v 516, the inner right-hand Contact ot relay 519, Wiudinfeot slow-toielease relay 519, and the lett-hand normal ycontact of relay 521 to ground. Relay 518 energizes and loclis through its inner lett-hand contact and Winding; to 1ground at the lett-hand normal contact oit' relay r1Ehe enerefization ot relay 51S closes.` at its right-hand alternate contact, an obvious locking; circuit for relay 504i.

As the brush 627 approaches the end of its revolution and disenoages segment 633, relay 516 is released, together with relays and 6.10, which were held energized by the saine ground which caused the operation oiI relay The release ot relay (S053 opens a lioldinoj circuit tor relay 600 vwhich thereupon restores to again connect start conductor 512 to the stepping' magnets 604-. G05 and 606.

lhen the code ot impulses is received by the mechanism of Fig. 8 locking relays 800, 801, 803., 805 and 806 are operated to can s the energization of associated pyramid relays which select the conductor 84.9. An impulse orn negative 120 volt polarity is then connected to the conductor 849 and extended to ground through the left-hand Windinni of the diilerential relay 721 to operate this relay, which thereupon locks through its right-hand Winding. rThis impulse ot current is also extended over the conductor Sil-9 to ground through the lett-hand winding' ot differential relay 729, which also opcrates but immediately releases upon the termination oi" the impulse inasmuch as no lockingcircuit is established for this relay, relay 726 being,r now in normal condition. The operation ot relay 729, at this time, performs no 'fonct-ion. Energization ot relay 721 establishes a circuit extending tlroin Igrounded battery through the windings ot busy signal magnets 718, 719 and 720 in series. and the lett-hand alternate contacts of relay 721 to ground. The lousy signal magnets are operated to indicate before the Various outward jacks at office Z the busy condition ot the toll line L. rlhe energization of relay 721 also establishes a circuit to light the lamp 730 before the in operators position and individual to line L. said circuit extending from `grounded battery through the lamp 730. the lett-hand contact ot relai7 731. the outer left-hand contact ot relay 704, the left-hand contact of relay S. and the outer left-hand contact ot relay 721 to ground.

In operator at 077706 Z marce/rs 257i@ incoming @all on Zine L.

The in operator, observing the lighted condition oit lamp 7 30, inserts the plug` 700 or a cord circuit A into the jack 7 32 and thereby establishes a circuit eatendinaF from grounded battery through the lett-hand Winding of relay 7 04e-, Winding` of relay 731, sleeve contacts of jack 732 and plug 700, and the Winding' of relay 702 to ground. Relays 702, 731 and 704 operate in this eircuit, the opening' of the lett-hand Contact of relay 781 and the outer lett-hand contact of relay 704C breakingthe circuit for lamp 730. which is thereupon extinguished. The operation of relay 7 O41 also establishes an energizing circuit 'for slow-to-release relay 726 extending from grounded battery through the Winding' of relay 726. the nor mal contact of relay 729, the right-hand Contact ot relay 704, and from thence to `ground through the lett-hand contacts ot relay 721. this ground also pr widineh a lockino; circuit for relay 7041-. rlhe operation ot relay 726 at this time performs no function. The operation ot relay 7 31 also establishes a circuit extending from grounded battery through the right-hand Winding of relay 705, the alternate contact of relay 731, the normal contact ot relay 728, and from thence in 'series through the right-hand normal rontacts of relays 725 and 703 to ground. Relay 705 energizes but its operation at this time has no effect except to connect ground through its inner right-hand contact to the windings ot the busy signal magnets 718, 719 and 720, which have already been operated by the energization ot relay 721.

The operator at oliice Z, upon actuating her listening key 7111, connects her telephone set to line L and thereby establishes a tall# ing connection with the operator at oilice X who has previously operated her listening ley 141. Upon ascertaining the number of the desired party from the operator at oiiice X, the operator at o'licice Z then proceeds to complete the connection in a- Welllnoivn manner through apparatus which forms no part ot the present invention.

Operator at ao@ X stom/.ZS t/Lc operator at oce Z after the connection llos bcc/n, established.

When the calling subscriber terminates the call the operator at office X receives a disconnect signal in a manner Well known in the art, and upon receiving this signal she transmits another signal to the oiiice Z Which is the same as the one transmitted When first establishing the connection. This signal is sent by the operator at ottice X pressing the ringing key 140 in the cord circuit A in response to which the relay 106 is energized to again cause the operation of relay` 107 which in turn operates relay 108, the latter relay then locking as before described. Upon the release ot the ringing key relays 106 and 107 release, and upon the closure ot the normal contacts of the latter relay the start conductor 112 and the individual conductor 113 are again `grounded as previously described, it being recalled that the relay 105 is at this time energized and locked to ground at the outer left-hand contact of relay 110, Which is also locked under the control of the lefthand normal contact of relay 111. The grounding ot conductors 112 and 113 initiates the operation o1' the mechanism of 2 to transmit the same code of impulses to the mechanism of Fig. 4C, which Was transmitted when the call was iirst initiated.

The translating mechanism of Fig. Ll, including the locking and pyramid relays, then operate to again select the conductor Llsf- 9 and apply thereto a negative impulse oit' 120 volt polarity Which is extended to ground through the left-hand Winding` of relay 500. This impulse has no etl'ect on thisv relay since the same is already operated and locked. The impulse is further extended through the outer lett-hand alternate Contact of relay 500, and from thence through the righthand Winding of relay 507 to ground. The relay 507 now operates and locks in a circuit traceable from ground` through the letthand Winding of said relay, the right-hand contact thereof, and the contact of relay 508 to grounded battery, this latter relay, together With the relay 308, having been energized when connection was first established and being held energized under the control ot relay 519. In energizing, relay 507 opens, at its normal contact, the holding circuit for relays 308 and 508, and these relays', after an interval, restore, the release of relay 508 opening the locking` circuit for relay 507, which thereupon releases. The operation and release of relay 308 perform no function While signals are being transmitted trom oiiice X to ofce Z but accomplish the same results as just described in connection With relay 508 when signals are being transmitted trom otiice Z to office X. While relay 507 is energized and locked under the control of relay 508, a circuit is established for sloW-to- Y release relay 522 extending from grounded battery through the Winding of said relay, t-he lett-hand alternate contact of relay 507, the normal cont-act ot relay 503, and the outer right-hand contact of relay 519 to ground, the latter relay having previously been energized under the control of relay 517 and locked under the control ot' relay 521. Relay 522 operates and in closin'g its alternate contact establishes an energizing circuit for relay 517 Which again locks. Following the release of relay 507 relay 522 restores Where-upon start conductor 512 and individual conductor 513 are grounded under the control of alternate contacts of relay 517 and normal contacts of relay 522. The grounding` ot the conductors 512 and 513 again initiates thev operation ot the sending mechanism of Fig. 6 to transmit to the receiving mechanism of Fig. 8 the same code ot' impulses that was transmitted from office X to oiiice Y. This code of impulses, upon being received at office Z, is translated to select the conductor 849 and apply thereto an impulse of negative 120 volt polarity, which now causes the operation of relay 7 29, Which then locks through its right-hand Winding and contact to ground at the contact ot rela-y 726. The opening of the normal Contact ot relay 729 opens the holding circuit for relay 726, which then restores. This relay being slow to release, the locking circuit for relay 729 ivill be maintained an appreciable interval. During this interval a circuit is established tor the slow-toerelease relay 733 extending from grounded battery through the Winding of relay 733, the left-hand alternate contact of relay 729, the right-hand contact ot relay 7 04, which is now operated and locked, and from thence to ground through the left-hand contacts ot relay v721, which is also operated and locked. Relay 733 energizes in this circuit and thereby connects ringing current to the line L over a circuit extending from a` source ot ringing current through the lower alternate Contact ot relay 733, the ring contacts ot jack T32 and plug 700, condenser 7 34, the iight-hand winding ot the ringing response relay 735, tip contacts ot' plug 700 and jack 732, and the upper alternate contact of relay 733 to ground. llelay 735 responds to the ringing` current thus applied to the line and locks through its lett-hand winding and contact to ground at the Contact ot relay 702. Following the locking ot relay 735, relay 733 releases to disconnect ringing current trom the line. The closure ot the contact of relay 735 establishes an obvious circuit tor lighting the supervisory lamp 736. The operator at oiiice Z responds to the lilghting ot this lamp by throwing her listening key '741 which places lier in communication with the operator at otlice X.

The operators may now converse and on being informed by the operator at ottice X that the call has been terminated by the calling subscriber, the operator at otlice Z removes the plug 700 trom the jack 732. This act causes the release ot relays 702, 731 and 735 and the extinguishment ot t-he lamp 736. The release of relay 731 ope-ns the previously described circuit for relay 7 05 which operated but performed no tune-tion at the time that the in operator originally responded tov the call.

After giving the disconnect signal the operator at otlice X removes the plug 100 from the jack 101, whereupon relays 102 and 103 release. Relay 104, which originally operated in series with relay 103, remains energized in the locking circuit described theretor. A condition now exists wherein relays 104, 105, 110 and 120 are operated. Due to the deenergization ot relay 103 a circuit is now established tor the release control relay 111 extending troni grounded battery through the lett-hand contact ot relay 109,v

the winding olf relay 111, the right-hand contact of relay 110, the right-hand normal contacts ot relays 137 and 131 in series, the normal contact ot relay 128, and the i'ight-hand normal contacts ot relays 125 and 103 in series to ground. Relay 111 energizes and locks to ground through its inner lett-hand contact. 1n operating, relay 111 disconnects `ground trom its lett-hand normal contact to open the locking circuit for relay 110, which, after an interval, releases and thereby breaks, at its outer lett-hand contact, the original locking circuit tor relay 105. Beitoie this Contact is opened, however, the outer lett-hand alternate contact of relay 111 is closed to maintain the locking circuit for relay 105. '.lhe closure ot the out- LO aA er right-hand alternate contact oit relay through the inner right-hand contact of relay 107. rllhe closure ot' the inner right-hand circuit extending trom ground through the winding ot relay 258, the mentioned contact ot relay 107, the outer right-hand contact of relay 105, and the individual conductor ual to line L over which wigei' 207 ot switch D passes. The grounding of the start nets 204, 205, and 20G to operate and step the wipers ot switches B, C and D over their 207 engages the terminal to which conductor is connected, relays 203 and 258 opereo causes the wipers ot switches B, C and D to come to rest upon the terminals individrelay 258 also operates to establish an obvious energizing circuit for relay 243, which,

connects negative potential to segment 242 ot the sending distributor SD. The euerenei'gizing circuit for relay 200 which, in operating, disconnects the start conductor 112 B, G and D. The operation ot relay 203 also initiates the operation of switch E, as

switch thereupon come to rest upon the desired terminals when the wiper 212 engages through the relay 258, conductor 113, wiper 20'! and the rightdiand contact of relay 203.

inaneiitly open the circuit ot the stepping magnet 211 and to close the circuit tor oping distributor. A code of impulses :is now transmitted troni otiice X to the receiving code is the same as that originally transmit ted when the call was initiated with the extiolled by the relay 243, said impulse being now negative instead ot positive. As this distributor RD, locking relays 400, 401, 403, 405, 406 and 407 are operated, the operation of the upper contact ot polar relay 450 in response to the eighth impulse ot negative the brush 434 engages the segment 446. The pyramid relays now respond., as before deupoii an impulse of 120 volt current is connected to this conductor. inasmuch as re- 111 grounds the start conductor 112 alternate contact ot relay 111 establishes a ot relay 111, the outer right-hand contact 113 which is connected to a terminal individcoiiductoi' 112 again causes stepping niagassociated rows of terminals. Then wiper i3 I 0 in series, and the energization ot relay ual to the line L, as before described. The

in closing its right-hand alternate contact,

gization ot relay 203 again establishes the trom the stepping magnets ot the switches before described, and the wipers of this the terminal to which ground is connected This ground operates the relay 21.0 to pereratiiig the start magnet 228 of the sendinechanisin ot Fig. 4 at otlice Y, and this ception of the eighth and last impulse conseries oft' impulses is received by the receiving ot the latter relay being due to the closure polarity, this impulse being received when scribed, to select the conductor 449, wherelay 407 is now operated this impulse will be lfll of positive instead ot negative polarity. The result of the application ot' this positive impulse of 120 volt current will presently be described.

As the brush 227 of the sending distributor is revolving, relays 208 and 210 are maintained energized as before by the ground connected to the ring 280 and segment 233, and this ground also operates relay 109. Relays 203, 210 and 109 remain energized until the segment 238 is disengaged by brush 227 at the termination of its revolution, whereupon these relays release. When relay 109 energizes, the locking circuit tor relay 111 is opened and this relay restores. The removal of ground Jfrom the outer lett-hand alternate contact of relay 111, opens the locking circuit .tor relay 105 which then releases. Restoration of relay 111 also causes the release of relay 258. The release of relay 105 is followed b v the release ot relays 104 and 126 Which Were held operated by the ground at the inner right-hand contact ot relay 105. This ground also maintained the busy signal magnets 118, 119 and 120 operated and these magnets therefore release upon the deenergization of relay 105 to indicate the idle condition oit the toll line L. The apparatus of Fig. 1 is now in its normal condition.

While the brush 227 is in engagement with segment 238 an obvious locking circuit for relay 243 is maintained, but after the eighth impulse of the series has been transmitted and the brush 227 has disengaged segment 238, the looking circuit tor relay 248 is opened and this relay thereupon releases. Relays 200, 203 and 210 also release as soon as the brush 227 disengages the segment 233. Therefore, as soon as the brush 227 completes its revolution the apparatus ot Fig. 2 is in its normal condition. The receiving mechanism of Fig. 4 is restored to normal in the same manner as previously described.

The positive impulse ot 120 volt current which is connected to the conductor 449 causes the release oit diliferential relay 500, whereupon a. circuit is established for the release cont-rol relay 521 extending from grounded battery through the left-hand normal contact of relay 516, Winding of relay 521, the outer left-hand contact of relay 518, Which is now energized and locked, the left-hand normal contacts of relays 502, 501 and 500 in series, and the outer normal contact of relay 509 to ground. Relay 521 energizes and looks through its Winding and inner lett-hand alternate contact, and, in opening its left-hand normal cont-act, breaks the locking circuit for relay 518, which relay, after an interval, restores. The opening' of the right-hand alternate Contact o't relay 518 interrupts the original locking circuit :tor relay 504, but before relay 518 can release a. substitute locking circuit is provided for relay 504 by the connection of ground to the outer lett-hand alternate contact of relay 521. Relay 504 therefore remains operated. The energization of relay 521 also opens, at its left-hand normal contact, the locking circuit for relay 519 which relay thereupon restores. The removal of ground from the outer right-hand contact of relay 519 breaks the holding circuits for relays 308 and 508, which Were operated a second time when the relay 507 released following the opening of the locking circuit for relay caused by the release of relay 508. The second operation of relays 308 and 508 performs no functions. In response to the opening of the holding circuit for relays 308 and 508, the-se relays restore to normal. Relays 504 and 521 are now the only relays at the intermediate otlice which are operated. The closure of the outer right-hand alternate contact of relay 521 grounds the start conductor 512 through the outer normal co-ntact of relay 522. When relay 521 energizes, the individual conductor 513 is also grounded through relay 658, the inner right-hand alternate contact of relay 521, the inner normal contact of relay 522, and the inner right-hand alternate contact of relay 504. The ground on the conductor 513 is extended to the terminal over Which Wiper 607 of switch D passes. In the same manner as previously described in connection With the transmission of the last code of impulses from F ig. 2, the apparatus of Fig. 6 responds to the grounding of the conductor 512 to transmit this same code ot impulses to the receiving mechanism at office Z. l/Vhen Wiper 607 of switch D engages the terminal to which the conductor 518 is connected, relays 603 and 658 cpe-rate7 the operation of the latter causing the energization of relay 643 to connect negative current to the segnient 642 of the sen-ding distributor SD. The receipt of the series oi' impulses by the receiving mechanism Pt-D1 results in the operation oil the locking relays 800, 801, 808,`

805, 806 and 807, the operation. of the latter relay resulting from the connection of negative polarity to the segment G42 ot the sending distributor SDl. The pyramid relays controlled by the operated locking relays are now energized to again selectthe conductor 849, whereupon an impulse o't positive. 120 volt current is connected through the righthand alternate contact of relay 807 to the conductor 849, and through the left-hand Winding ot differential relay 721 causing the release ot the latter relay. This positive impulse has no effect upon the differential relay 729. At the termination oit the. iinpulse. the mechanism ot F ig. 8 is restored to normal in the manner previously described. The release of relay T21 disconnects ground through its lett-hand alternate contacts from the windings o' the` busy signal magn nets T13, 71S) and 720, whereupon these magnets release to indicate an idle condition out the line L beiore the outward jacks at otlice Z. The opening of the lett-hand alternate contacts ol relay 721 also breaks the locking circuit Jfor relay 704 a d the holding circuit for relay 726, these relays there-upon restoring to normal. lhe apparatus of Fig. 7 is now in its normal condition. VJhen the brush S2? ot the sending distributor SDl engages the segment 63S, a holding circuit is provided tor relays 603 and 010, a locking circ-uit is established for relay e423 and relay 516 is energized. The operation ot the latter relayY opens thel locking circuit for relay 521 which, in restoring, disconnects ground from the locking Winding ot relay 504, whereupon this relay releases. The apparatus of Fig. 5 is then in its normal condi tion. The release of relay 521 causes the deenergization et relay 058 but relay 043 re mains ope-rated in its locking circuit. 'Vhen brush 62'? disengages the segment 683 the relays G00, G08. G10 and G43 restore in a manner which is now believed to be obvious, thus leaving the apparatus ot Fig. 0 in its normal condition.

Let it be assumed for the purpose ot describing this portion ot the operation ot the circuit that a call has been originated at ottice Z and extended to otice X. 'In this event the operation ot signaling the in7 operator at ottico X is exactly the same as that already described in connection with the extension ot an original call from. oflice X to otlice Z. ln Fig. T, which is a duplicato o't Fig'. 1, relays correspond'ng to relays in Fig. 1 and similarly numbered, ef;- cept tor the hundreds digits, operate in the saine manner and produce the same results as Were described in connection with th latter relays. is a result ot the insertion oi" plug T00 ot the cord circuit A into the jack 701 and the consequent operation of the relays in Fig. 7, a sending mechanism indicated by the rectangle SDE, and similar in all respects to that shown in Fig, 2, operates to transmit the code oi impulses individual to the lineL and to the in operators position at otlice X to the receiving mechanisin indicated at RD?. The conductor 540 is thereby selected and the 120 volt impulse oit current oit negative polarity applied to said conductor operates the relay 300 individual to the in operators position. From this point the operation is the saine as that described in connection With Fig. 5, the relays in Fig. 3 involved in this operation heilig numbered the same as those "n F. 5. with the exception o'li the hundreds digits. Thel operation oit the nieclninisni ot and 313, with the result that a send'ng mechanism represented by the rectangle SD and similar in all respects to the apparatus shown in Fig. 2, is operated to again transmit the code of impulses individual to the line L and to the in operators position. This code is received by the mechanism indicated at RD, similar to the receiving mechanism of Fig. 4, which then operates to select a conductor 149 in the same manner that conductor 849 was selected. Relay 121 is then energized in the saine manner that relay 7 21 was operated. Frein the previous description ot' operation resulting in the energization of relay 721, it is believed that the eiectof the operation oi relay 121 will be readily understood, it being borne in mind that reference characters applied to like parts in Figs. 1 and 7 are the same `vwith the exception of the hundreds digits.

The occasion tor an operator at otlice X calling the out operator at oiiice Z arises when the in operator at oliice X, on call incoming to this ot'lice, fails for some reason to secure a connection to the Wanted subscriber. lin this event she informs the calling operator at otlice Z of her inability to complete the connection to the desired party and transfers the ticket or record of the call to the out7 or delayed call operator at oiiice rlhe originating or zalllng operator at otlice Z, upon being informed by the in operator at ottico X that connection to the Wanted line cannot be obtained, also transfers the record of the call to the "out7 or delayed call operator at her o'tlice. The out or delayed call7 operator at oiire X then endeavors from time to time to secure a connection to the Wanted party, and when successful proceeds to call the out or cdelayed call7 operator at otlice Z who then signals the calling subscriber after u'hch the call is completed in accordance with Well-known practice.

To signal the Cout operator at o'l'tice Z, the Cout operator at otlice inserts plug of acord circuit A into a acl; 124 and thereby establishes a circuit eXtendng from ground through the Winding ot' relay 1027 sleeve contacts ot plug 100 and jack 124, the Winding of relay 125, and the letthand Winding of relay 104 to grounded battery. Relays 104 and 125 energize in series and the operation of the latter establishes a circuit i'or relay 116 extending 'from grounded battery through the right-hand Winding of said relay, the alternate contact ot relay 125, and the right-hand normal Contact o'lE relay 103to ground. The operation ot relay closes a locking circuit tor relay 104 by connecting ground to the inner righthand contact of relay 116 and the right-hand contact and winding of relay 104. The operation of relay 116 also closes, at its inner right-hand contact, an obvious circuit for operating busy signal magnets 113, 119 and 120 to indicate the busy condition of the line L.

The operator now depresses her ringing key 140 to energize relay 106 as previously described, whereupon relay 107 operates to establish the energizing circuit for relay 108, which thereupon locks. Relay 110 is also operated and locked as before. then the operator releases the ringing key, relay 106 restores to open the circuit vtor relay 107 which, after an interval, releases. llVhen relay 107 closes its normal contacts the start conductor 112 and the conductor 1:14, individual to the toll line L, are grounded, the circuit ior conductor 112 being the same as previously described, while the path for grounding the conductor 114 extends from ground through the outer right-hand contact of relay 108, the right-hand normal Contact l of relay 111, the outer normal contact of relay 107, the outer right-hand alternate contact of relay 116 to the conductor 114. The grounding orn start conductor 112 causes the operation of stepping magnets 204, 205 and 206, as previously described, whereupon the wipers or" switches B, C and D are stepped until ground is encountered upon one oit the terminals over which wipers 207, 208 and 209 pass. In the present instance this ground is 'found upon a terminal over which wiper 208 passes and to which conductor 114 is connected. Engagement with this terminal by wiper 208 closes a circuit for relay 202 extending from grounded battery through the right-hand winding or' said relay and the wiper 208 to ground on the conductorl 114. Relay 202 energizes to stop the operation ot stepping magnet 205 and on energizing closes the circuit for operating relay 200. The energizationlot the latter relay disconnects the start conductor 112 from stepping magnets 204 and 206. The wipers of switches B, C and D therefore come to rest upon their respective terminals which are individual to the line L. The energization of relay 202 connects ground from its letthand alternate contact to the common conductor extending to the contact and winding of the stepping magnet 211 through the normal contact of relay 210. The encrgization of relay 202 also extends the ground connected to wiper 208 through the right-hand Contact oi' relay 202 to certain terminals associated with wiper 212 or switch E. The closure of the circuit for stepping magnet 211 operates this magnet to step the wipers of switch. E 'from the terminals then engaged thereby until wiper 212 engages the first terminal in its bank to which ground is connected. Again assuming that the wipers of switch E are on the third terminals or their respective banks, it will be seen that said wipers will be caused to take two steps to the lift-h terminals thereof, at which time the wiper 212 encounters the ground through the right-hand cont-act of relay 202, which ground is then extended through the lett-hand winding of relay 210 to grounded battery. Relay 210 then operates to stop the operation of the stepping magnet 211 and the wipers of switch E thereupon come to rest upon the fifth terminals in their respective banks.

The apparatus is now in condition to transmit the code oi impulses individual to the toll line L and tothe out operators position at oiiice Z. This particular code of impulses is determined by the position ot the wipers 219 to 225 inclusive of switch E and the wipers 245 to 249 of switch C. lVith the mentioned wipers of Switchs E and C on the fifth terminals appearing on the drawing, it will be seen that the polarities of the first seven impulses of the present code are positive, negative, positive, negative, positive, negative and negative, transmitted in the order named. The eighth impulse is again determined bythe condition of the relay 243, which, in this operation, is normal as before described, thereby causing a positive impulse to be transmitted. By reference to the previous description it is believed that the operation ot transmitting this code ot impulses will be readily understood. As the impulses of the code are received by the receiving distributor RD, relays 401, 403, 405 and -406 are operated and locked under the control of relay 408. The energization of the above-mentioned locking relays causes the energizaticn of the pyramid relays 409, 412 to 415, and 420 to 426 in the manner now believed to. be obvious. With these pyramidA relays operated, when the brush 434 of the receiving distributor RD engages segments 447' and 443, a negative 120 volt impulse of current is transmitted from the source through the normal contact ot relay 407, segment 447, brush 434, segment 448, the right-hand alternate contact of relay 406, the right-hand alternate contact of relay 409, the lett-hand normal contact ot relay 411, the left-hand alternate contact of relay 414, the right-hand normal contact of relay 418, the right-hand alternate contact of relay 425, the left-hand normal contact of relay 430, conductor 451, and from thence through the lett-hand winding of the differential relay 501 to ground. This impulse of current causes relay 501 to energize and then lock through its righthand winding and inner right-hand contact. The effect oiZ the operation of relay 501 will presently be described. After the impulse of current has been transmitted brush 434 disengages the segment 440 and thereby 

